Axial flow compressors incorporating boundary layer control



April 19, 1960 E. A. STALKER AXIAL 110w COMPRESSORS INCORPORATING BOUNDARY LAYER CONTROL 2 Sheets-Sheet 1 Filed June 24, 1954 INVENTOR.

April 19, 1960 E. A. STALKER AXIAL. mow COMPR ESSORS INCORPORATING BOUNDARY LAYER CONTROL 2 Sheets-Sheet 2 Filed June 24, 1954 INVENTOR.

United States Patent AXIAL FLOW COMPRESSORS INCORPORATING BOUNDARY LAYER CONTROL Edward A. Stalker, Bay City, Mich.

Application June 24, 1954, Serial No. 439,110

'5 Claims. (Cl. 230-122) This invention relates to axial fiow compressors for elastic fluid.

An object of the invention is to provide a compressor whose blades have slots or other opening means in their surfaces at selected localities for controlling the boundary layer. g

Another object is to provide simple and eifective slot constructions for the blades.

Other objects will appear from the specification, drawings and claims.

' The above objects are accomplished by the means illustrated in the accompanying drawings in which- Fig. l is a fragmentary axial section of a compressor according to this invention; 7

- Fig. 2 is a fragmentary transverse section of a rotor on line 2-2 in Fig. l; r

i Fig. 3 isa fragmentary development of the blading of arotor upstream stage;

""Fig. '4 is a fragmentary development of the blading of a rotor downstream stage; 4

Fig. 5 is an enlarged section of an upstream rotor blade on line 5 5 in Fig. l; j Fig. 6 is a fragmentary'enlarged side view of a rotor blade;

Fig. 7 is an enlarged View of a nose rib isolated from a blade;

Fig. 8 is an enlarged section of a downstream rotor blade on line 8-8 in Fig. 2; and

Fig.9 is a fragmentary chordwise view of a front beam of a blade.

, In a compressor rotor the blades may be placed closely together about the periphery of the rotor hub so that the flow is constrained to follow the upper or convex sur- The blades as shown particularly in Figs. 1, 3 and 5 each have an opening means such as for instance a slot 65 positioned between the leading edge L.E. of its blade and the normal projection 68 thereon of the following blades leading edge. That is the slot is in the nose portion 6869 of the upper surface. Preferably the slot is at or closely adjacent to its blades leading edge and extends along a major portion of the radial extent of the.

blade. The slots lead out of the hollow interiors 70 of the blades. A rim means 58 is carried on the hub of each rotor at the radially inner ends of the blades and extends in closed relation from blade to blade and from the leading to the trailing edges of each blade to sustain in conjunction with the case 12 the static pressure rise in each stage.

These upstream blades 50 have their hollow interiors in communication with the hollow interiors 72 of the blades 54 of rotor 22 through the radially inner ends of said blades, the manifolds 73, 74 and channels 80 formed in the hub as shown in Figs. 1 and 2. There are four such channels 80 spaced peripherally about the rotor.

The interiors of the blades of rotors 21 and 23 are in communication through the manifolds 75, 76 of channels.

82 shown in Figs. 1 and 2.

The blades 54 of rotor 22 have induction slots 84 in the surface preferably nearer to its blades leading edge at the rotor 20, fluid will enter the slots of the blades 54' and flow forward in channels 80 to the slots 65 issuing therefrom as rearward directed jets.

The inward flow into the slots 84 of blades 54 will control the boundary layer and enable the blades to operate at larger angles of attack. Also the jets from slots 65 will control the boundary layer and enable the blades to operate at larger angles of attack.

In like manner the flow into the slots 86 of blades 56 v and out of slots 87 of blades 52 will control their respective boundary layers and enable the blades to operate at faces of the blades even for large curvature in the aft portions of the blades. This 'ability'of the flow to cling to the convex surface is also aided bythe centrifugal action on-the boundary layer which causes it to flow radially outward to blade sections of lower camber.

{ When these conditions prevail the portion of a blade from which the flow may most readily separate is that ahead of the projection thereon of the leading edge of the adjacent blade. A slot or other opening means will be most effective if located in the blade chordwise between its leading edge and the normal projection thereon of the leading edge of an adjacent following blade. Preferably the slot should be close to its own blade leading edge.

Referring now to the drawings the compressor is indicated generally as 10. -.It comprises the case means 12 which houses the rotor assembly 14. This assembly in turn cornprisesthe-rotors 20 23. g g

The case 12 supports the stators*2629 each positignedrearward of a rotor. The stators comprise a plurality of stator blades 30-33.

Thefluid tobecompressed by the compressor enters therannular inlet 40 and is discharged from the annular exit42; 1

larger angles of attack.

The hollow interiors of the stator blades of the front two stators are respectively in communication with the hollow interiors of the blades of the two rear stators 28 and 29. The blades 30 and 31 have discharge slots and the blades 32 and 33 have induction slots.

The interiors of stator blades 30 are in communication with the interiors of stator blades 32 by way of manifolds 88, 89 and channel 90.

The interiors of stator blades 31 are in communica tion with the hollow interiors of stator blades .33 through manifolds 98, 39 and channels 92. For this purpose the rear ends of these channels are open into the space 93.

See Fig. 2.

The blades 50 and 52 with discharge slots are prefer-.

ably formed as shown in Fig. 5 for blade 50. Each blade comprises an upper surface and a lower surface 102 fixed together at their rear ends. They are spaced apart at their front ends to define the discharge slots 65.

by the beams 104 and 106 ticularly in Figs. 5 and 6. A rib 108 is shown isolated Patented Apr. 19, 1960.

3; .7 in Fig. 7. The flanges 109, 110 and 111 of the ribs are preferably soldered to the beam1li4 and the surfaces 100 and 102. I

The blades 54 ,and 56 are substantially alike, 'As shown in Fig. 8 blade 5 comprises the upper surface 112 and the lower surface 113 one supported on the other at their rear ends and by beams 13- and 116 as well as by ribs120.

Preferably the induction slots are defined by the front ends of the upper and lower surfaces as shown in Fig. 8. This positions the slots as close as about the thickness of a surface to the leading edge LE. It is an economical method of defining the slot since the forming of the front edges of the surfaces is a simple operation.

The beams 104 and 114 are placed close to the leading edges of their blades to relieve the nose portions of the blades of bending stresses. Each beam has openings 136 for the'passageof fluid from one side thereof to the other.

As shown in Figs. 35 and 8 the blades preferably have-ahigh arching of their mean camber lines 140 with the maximum camber ordinate 141 preferably as far back as the mid chord point or still further rearward. Preferably the mean camber line is about normal to the plane of rotation at its aft end and the mean camber maximum ordinate is preferably greater than 8 percent of the blade chord (143) length.

The blades are placed close together peripherally so that boundary layer slots may be omitted within the rotor passages between blades defined at their ends by the projection of the leading and trailing edges onto the adjacent blades normal to their surfaces. See Fig. 3. Preferably the peripheral spacing is such that the leading edge of a following blade of any pair of blades is at or, chordwise forward of the mid chord point of the leading blade of said. pair.

' angles of attack.

It will now be clear that I have disclosed a novel and effective means for obtaining a large range of angles of attack for compressor blades.

While I have illustrated specific forms of the invention, it is to be understood that variations may be made therein and that I intend to claim my invention broadly as indicated by the appended claims.

7 I claim:

1. In combination in an axial flow compressor for increasing the pressure of an elastic fluid, said machine providing a source of fluid under pressure, a case, a rotor mountedin said case for rotation about an axis, .said rotorcomprising a hub and a plurality of axial flow blades having hollow interiors peripherally spaced thereabout and carried thereon with flow passages between saidblades said blades extending radially outward from said hub with respect to said axis, each said blade having an eduction slot in the convex surface thereof positioned closer along a major portion of the length of said slot to the leading edge of said blade than to the normal projection thereon of the leading edge of an adjacent said blade, rim means on said hub at the radially inner ends of said blades extending in closed relation from the leading to the trailing edges of each blade and from blade to blade to sustain a pressure rise in said rotor,

means for causing a flow of fluid through said slot from a zone of different pressure, each said slot extending along a major portion of the radial length of each said 2. Incombinati0nfin an axial flow compressor for in 7 the main flow of fluid about said blades on the portionv thereof ahead of said projection.

creasing the pressure of an elastic fluid, a case, a rotor mounted in said case for rotation about an axis, said rotor comprising a hub and a plurality of axial flow blades peripherally spaced thereabout and carried thereon with flow passages between said blades, said blades extending radially outward from said hub withrespect to said axis, each said blade having a suction slot in the convex surface adjacent the leading edge thereof extending'alo'n-g a major portion of the radial length of each said blade and being positioned closer along a major radial length of said slot to the leading edge of said blade than to the projection thereon of the leading edge of an adjacent said blade, r-im means on said hub at the radially inner ends of said blades extending in closed relation from the leading to the trailing edges of each blade and from blade to blade to sustain a pressure rise in said rotor, means for causing a flow of fluid through said slot from a zone of different pressure, each said slot being in communication through the radially innenend of its respective said blade with the interior thereof and with .said flow-causing means for the induction of a flow higher fluid pressure at said downstream rotor than the fluid pressure at said upstream rotor, each said rotor comprising a hub and a plurality of axial flow blades peripherally spaced thereabout and carried thereon with flow passages between said blades, saidblades extending radially outwardfrom said hub with respect to said axis, each said blade of an upstream rotor'having a hollow interior and a rearwardly directed discharge slot in its upper surface in communication with said interior, each said blade of a downstream rotor having a hollow interior and an induction slot adjacent the leading edge thereof leading into said interior, and means of communication between said interiorsof said upstream blades and said interiors of said downstream blades to conduct a flow of said fluid into the interiors of said downstream blades and out of the interiors of said upstream blades, each said slot extending along a major portion of the radial length of its respective said blade, said slot in each said blade being closer along a major portion of the radial length thereof to the leading edge of said blade than to the normal projection thereon of the leading edge of a peripherally adjacent said blade, to control 4. In combination in an axial flow elastic fluidcompressor for increasing the pressure of an elastic fluid, a case, a rotor mounted in said case for rotation about an axis, said rotor comprising a hub and a plurality of axial flow compressor blades peripherally spaced thereabout and carried thereon with flow passages between said blades, said blades extending radially outward from said hub with respect to said axis, each said blade comprising a convex wall and a concave wall supported one. on the other in spaced'relation defining a hollow interior.

and a rearwardly directed slot in said convex surface adjacent the leading edge thereof, said surface also defining external contours of said blades, said slot being displaced rearward from said leading edge by a distance equal substantially to the thickness of said surface, a

spanwise beam within said blade closely adjacent to said slot and fixed to said convex and concave walls along a major portion of the radial extent of each said blade, each said blade including means of communication be tween said slot and the portion of the interior of said blade on the side of said beam opposite tosaid-slot, said means being distributed along a major port on of the radial extent of said blade, and fluid pressure means in communication with said slot and said blade interior through the radially inner end of said blade to cause a flow through said slot.

5. In combination in an axial flow compressor for increasing the pressure of an elastic fluid, a case, a rotor mounted in said case for rotation about an axis, said rotor comprising a hub and a plurality of axial flow blades peripherally spaced thereabout and carried thereon with flow passages between said blades, said blades extending radially outward from said hub with respect to said axis, each following blade of any pair of said blades having its leading edge forward of a mid chord point of a leading blade of said pair to induce said fluid to follow the surface of said blades and leaving a front portion of the convex surface of said leading blade uncovered by said following blade, said uncovered front portion of the convex surface of said leading blade lying between the leading edge thereof and the normal projection of the leading edge of said following blade on the surface of said leading blade, each said leading blade having radially directed slot in said uncovered portion extending along a major portion of the radial length thereof with a major portion of the radial extent of said opening means closer to the leading edge of said leading blade than to the normal projection thereon of the leading edge of the peripherally adjacent said blade, means in said hub defining a channel for conducting fluid at a lesser pressure than that of said fluid outside said blade adjacent said uncovered portion, said channel being in communication through the root end of each said blade with the hollow interior of each said blade and said opening means thereof to extend the range of operation of said blades.

References Cited in the file of this patent UNITED STATES PATENTS 2,136,403 Vance Nov. 15, 1938 2,314,058 Stalker Mar. 16, 1943 2,344,835 Stalker Mar. 21, 1944 2,405,768 Stalker Aug. 13, 1946 2,501,614 Price Mar. 21, 1950 2,514,105 Thomas July 4, 1950 2,527,971 Stalker Oct. 13, 1950 2,656,146 Sollinger Oct. 20, 1953 2,663,993 Mosser Dec. 29, 1953 2,678,537 Stalker May 18, 1954 2,685,405 Stalker Aug. 3, 1954 2,780,435 Jackson Feb. 5, 1957 FOREIGN PATENTS 89,723 Sweden July 13, 1937 758,906 Great Britain Oct. 10, 1956 904,610 Germany Feb. 22, 1954 1,007,303 France Feb. 6, 1952 

